Supercharger assembly

ABSTRACT

A vehicle supercharger assembly ( 110 ) comprises a dual generator comprising first and second co-axial relatively rotatable armatures ( 14   a,    14   b ), and a first disengageable clutch ( 32 ) between the armatures ( 14   a,    14 ), said first armature ( 14   a ) being adapted for permanent drive from a source of motive power, and said second armature ( 14   b ) being driven by said first armature ( 14   a ) on engagement of said first clutch ( 32 ); a supercharcharger impeller ( 24 ), the second armature ( 14   b ) driving the impeller ( 24 ) mechanically via a gear train; an electric motor coupled to the gear train and operable to adjust the rotational speed of the impeller ( 24 ); wherein, in use, the electric motor is electrically driven on demand from a generator comprising the second armature ( 14   b ).

RELATED APPLICATIONS

This application is a 35 U.S.C. § 371 national stage application of PCTApplication No. PCT/EP2013/062404, filed on Jun. 14, 2013, which claimspriority from Great Britain Patent Application No. 1210679.5, filed onJun. 15, 2012, the contents of which are incorporated herein byreference in their entireties. The above-referenced PCT InternationalApplication was published in the English language as InternationalPublication No. WO 2013/186373 A1 on Dec. 19, 2013.

FIELD OF THE INVENTION

This invention relates to a supercharger assembly for an internalcombustion engine and in particular, but not exclusively, to electricdrives comprising a generator and motor in combination and a controlmethod for the same. Aspects of the invention relate to a generator, toa supercharger assembly, to a control unit, to a method and to avehicle.

BACKGROUND

Exhaust-driven turbochargers are typically provided for internalcombustion engines in order to improve their performance by increasingthe pressure, temperature and density of air in an engine inlet manifoldwhich is used to supply a fuel/air mixture to the engine cylinders. Thismakes it possible to burn more fuel in each cycle of the engine, therebyincreasing the power output. Exhaust-driven turbochargers make use ofenergy contained in the engine exhaust gases which would otherwise go towaste, and therefore can contribute to an improvement in the overallefficiency of the engine. However, single-stage turbochargers are notparticularly effective at the low rates of exhaust gas flow which areassociated with low engine operating speeds. This leads to the problemof ‘turbo lag’, i.e. a noticeable delay between a driver demanding powerand the engine delivering the required response, because the enginespeed needs to rise to a certain level before the turbocharger operateseffectively. These problems can be ameliorated to some extent by the useof multi-stage turbochargers.

An alternative solution is to provide a supercharger in addition to theturbocharger. The supercharger is driven mechanically by the engine, toperform the same task of raising the pressure, temperature and densityof air in the inlet manifold when the engine is running at low speedssuch that the turbocharger is ineffective. A supercharger is engaged atthe instant of a driver demanding power to substantially increase thevolume of air admitted to the engine. With appropriate fuelling, asupercharger can eliminate turbo lag. An additional benefit is that theimmediate increase in air flow allows the turbocharger impeller to spoolup more quickly than would otherwise be the case. However, as thesupercharger is driven mechanically by the engine, it increases the loadon the engine and thereby increases fuel consumption. Therefore, as soonas the turbocharger is effective, the supercharger may be deactivated.

Control strategies have been developed for operating a supercharger andturbocharger both sequentially and simultaneously, so as to provide thedesired range of engine performance and engine response.

Superchargers may be driven directly from the vehicle engine, but thisarrangement tends to be inflexible should the installation envelopechange, for example because the engine is to be fitted to a differentengine compartment. Accordingly, it has been proposed to drive thesupercharger mechanically via the armature of the vehicle generator,which provides for different installation possibilities within an enginecompartment.

In one arrangement the supercharger is mounted co-axially with thevehicle generator, which is in turn driven by the vehicle engine by amulti-vee belt which is mounted on a pulley which is coupled to thegenerator. The generator provides energy to the vehicle, and thearmature of the generator is coupled mechanically to the superchargervia an epicyclic gearbox so as to provide a coaxial arrangement whichincreases the speed of the supercharger relative to the generator.

An epicyclic gearbox is composed of an outer gear ring or annulus, aplurality of inner planet gears referred to below simply as planets, anda central gear or sun. The sun is located at the centre of the annulus,with the planets located between, and meshing with, both the sun and theannulus. The planets are attached to a common planet carrier, whichmaintains their relative positions. If the planet carrier is rotatedwhile the annulus is held stationary, the planets are caused to rotatearound the inner surface of the annulus. As the planets rotate, this inturn causes the sun to rotate at a speed which is determined by thegearing ratio. Alternatively, the planet carrier may be held inposition, in which case rotating the annulus causes the sun to rotate.In this way, the epicyclic gearbox provides a coaxial arrangement whichgenerates the required speed.

The speed at which the vehicle engine operates is variable within arange of, for example, 500 to 7000 revolutions per minute (rpm). In thecase where the planet carrier is held stationary, the arrangementdescribed above produces a speed increase of around 30:1, through acombination of a 3:1 increase from the pulley, and a 10:1 increase fromthe epicyclic gearbox. Therefore, the expected operating range for thesupercharger impeller in this arrangement is 15,000 to 210,000 rpm.However, in order to achieve optimal performance, it is desirable tomaintain the speed of rotation of the supercharger impeller at arelatively constant level during operation, generally at around 120,000rpm.

To this end, it has been proposed to couple the planet carrier of theepicyclic gearbox to an electric motor. By driving this motor forward orin reverse, as required, the speed of the supercharger can be adjustedto its optimal level. Power for the supercharger motor is provided fromthe vehicle generator, which is necessarily increased in size. Thisarrangement provides the benefit that the main work of driving thesupercharger is performed by the vehicle engine, while the electricmotor merely provides a fine-tuning action. The power requirement of thesupercharger is such that it is impractical to attempt to use anelectric motor in isolation to drive the supercharger in a vehicleenvironment.

If a supercharger is used in combination with a turbocharger, thesupercharger is primarily active when the engine is operating at lowspeed, for example when the vehicle is pulling away. Once the enginespeed is sufficient, the turbocharger takes over from the supercharger,as this saves on energy requirements. In the above-describedarrangement, the supercharger is directly connected to the generator,and is thus constantly driven even when not being used. However it canbe made to idle by, for example, opening the delivery side toatmosphere. This reduces the load on the supercharger impeller, andtherefore in turn the energy which the supercharger draws when idling isreduced.

However, this arrangement retains the disadvantage that the superchargeris permanently connected to the generator armature, and thus absorbssome energy even whilst deactivated. It is well known that energyefficiency is a key concern in the design and manufacture of newvehicles, and therefore any measures which can be taken to reduceconsumption are important.

Against this background, it is an aim of the invention to provide anarrangement that avoids idling of the supercharger, but maintainsflexibility of installation.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides a vehicle superchargerassembly comprising:

-   -   a dual generator comprising first and second co-axial relatively        rotatable armatures, and a first disengageable clutch between        the armatures, said first armature being adapted for permanent        drive from a source of motive power, and said second armature        being driven by said first armature on engagement of said first        clutch;    -   a supercharcharger impeller, the second armature driving the        impeller mechanically via a gear train;    -   an electric motor coupled to the gear train and operable to        adjust the rotational speed of the impeller;    -   wherein, in use, the electric motor is electrically driven on        demand from a generator comprising the second armature

The dual generator allows for electrical and mechanical connection of asupercharger on demand, thus avoiding idle rotation thereof. The sourceof motive power is typically a vehicle internal combustion engine. Inone embodiment the dual generator comprises a primary generatorcomprising said one armature for supplying conventional vehicle systems,and a secondary generator comprising said other armature for supplyingan electric motor of a supercharger.

By integrating the dual generator into a supercharger assembly, itbecomes possible to disengage the supercharger impeller whensupercharging is not required, in order to prevent idling of thesupercharger impeller. This reduces the load which is driven by thesource of motive power, thereby reducing fuel consumption of thevehicle. The electric motor provides the ability to adjust therotational speed of the supercharger impeller, in use, to an optimumlevel. The motor of the supercharger assembly may be bi-directional.

It will be understood that in addition to providing supercharging ondemand, the dual generator arrangement allows for supercharged andnon-supercharged variants of a vehicle engine, but with a common primarygenerator. Furthermore the secondary generator may be varied in capacityfor driving different superchargers associated, for example withgasoline and diesel derivatives of the same basic engine.

The second armature may be associated with a generating capacity equalto or greater than said first armature.

In one embodiment, the first and second armatures are journalled onewithin the other for rotation about a common axis.

Conveniently, the first clutch may be provided axially between saidarmatures.

One or both of the first and second armatures may comprise an electricmotor.

The impeller may be co-axial with the first and second armatures. Inthis embodiment, the impeller may be journalled in the second armature.

The dual generator may be operable as a dual motor to drive said sourceof motive power. In this arrangement, the dual motor may be operable inconjunction with said electric motor to drive said source of motivepower.

The gear train may be an epicyclic gear train. The second armature maydrive said impeller mechanically via the annulus and planets of theepicyclic gear train and said electric motor may drive the planetcarrier of the epicyclic gear train.

The supercharger assembly may further comprise a second clutch forselectively locking and unlocking the epicyclic gear train. In thisembodiment, the electric motor may comprise a third armature which isarranged coaxially with the first and second armatures, wherein theelectric motor provides variable, bi-directional drive to adjust therotational speed of the supercharger impeller when the epicyclic geartrain is unlocked by the second clutch.

The second clutch beneficially acts to lock the epicyclic gear trainwhich effectively couples the dual generator to the electric motor, thusenabling the two to act together to provide motive force. In the casewhere the electric motor comprises a third armature, the second clutcheffectively couples the second armature to the third armature when theepicyclic gearbox is locked.

The second clutch may be arranged to lock the epicyclic gear train suchthat relative rotation of the planets and the annulus is prevented. Inthis embodiment, the second clutch may be in the form of a dog clutcharranged to interengage the annulus and at least one of the planets.Disengagement of the dog clutch may be effected hydraulically.

The dual generator may be arranged to be operated as a motor to drivethe first armature, and the generator and motor are arranged tocooperate when the epicyclic gear train is locked by the second clutch,thereby to supply a drive force to a vehicle engine.

The electric motor of the supercharger assembly may comprise a thirdarmature which is coaxial with the first and second armatures, and asecond clutch between the third armature and the second armature, thethird armature being driven by the second armature on engagement of thesecond clutch, wherein the third armature provides additional generatingcapacity to the generator when coupled to the second armature when boththe first and second clutches are engaged.

Therefore the dual generator of the supercharger assembly of theinvention may be operated as a motor, optionally in conjunction with theelectric motor, in order to drive the vehicle engine, for example as abelt integrated starter generator (BISG) or as an anti-stalling measure.

The dual generator can provide additional driving capacity which may notbe available from a conventional generator sized only to meet the normalelectrical load of a vehicle.

The third armature may be operable as a secondary generator to increasethe overall generating capacity of the vehicle when the first clutch isengaged and the epicyclic gear train is locked by the second clutch. Inthis embodiment, the first, second and third armatures are effectivelycoupled to each other and therefore rotate together. This allows for anincrease in the generating capacity of the arrangement on top of thecapacity provided by the dual generator. This embodiment thereforeprovides a triple generator.

According to another aspect of the invention there is provided a controlunit for a supercharger assembly as described above, and comprising anelectronic control unit for controlling operation of the first clutch,the second clutch and the electric motor as appropriate, and forenabling the supercharger.

The control unit may determine coupling of said electric motor with thegenerator comprising the second armature.

The control unit may be further adapted to configure said dual generatoron a dual motor adapted to drive said source of motive power.

According to a further aspect of the invention, there is provided amethod of preparing for operation of a vehicle supercharger assembly asdescribed above, and comprising the steps of: (i) detecting arequirement for supercharging; and (ii) engaging the first clutch tomechanically couple the first and second armatures, and operating themotor to bring the impeller to a desired speed. The motor may beelectrically coupled to a generator associated with said secondarmature.

The invention also extends to a method of operating a vehiclesupercharger assembly as described above, and comprising theaforementioned preparing method, and the further steps of bringing saidsupercharger on load, and electrically varying the speed of said motorto maintain the output of said supercharger at a desired rate.

The invention also extends to a method of providing a belt integratedstarter generator comprising configuring the dual generator of thesupercharger assembly described above as a dual motor, and engaging saidfirst clutch.

The invention also extends to a method of providing an anti-stallingdevice for an internal combustion engine, the method comprising thesteps of configuring the dual generator of the supercharger assemblydescribed above as a dual motor, and engaging the first clutch. Themethod may further include using said dual motor and said electric motorin unison.

According to another aspect of the invention, there is provided a methodof operating a dual generator of the above described superchargerassembly, wherein the method comprises disengaging the first clutch inat least one of the following conditions: (a) during an enginecold-start procedure; and (b) when the vehicle is idling.

Operating the supercharger assembly in this way advantageously avoidsidling of the second armature and the supercharger impeller, when eitherof the listed conditions apply, thereby reducing fuel consumption.

For those embodiments including a second clutch, the method may furthercomprise unlocking the epicyclic gear train using the second clutch whenthe first clutch is disengaged. This beneficially places the secondclutch in the appropriate configuration for all of the operatingconditions that are likely to follow, therefore saving time when a newcondition is initiated.

According to another aspect of the, invention, there is provided amethod of operating a supercharger assembly as described above, whereinthe method comprises engaging the first clutch in any one of thefollowing conditions: (1) when the ambient temperature is low and theengine is idling; and (2) when the speed of the vehicle is decreasingand there is no torque demand placed on the engine.

Operating the supercharger assembly in this way advantageously increasesthe generating capacity of the arrangement by adding the generatingcapacity of the second armature when energy requirements are higher as aresult of one of the listed conditions applying.

For those embodiments of the supercharger assembly including a secondclutch and a third armature, the method may comprise engaging the firstclutch, locking the epicyclic gear train using the second clutch andoperating the third armature as a secondary generator in any one of thefollowing conditions: (1) when the ambient temperature is low and theengine is idling; and (2) when the speed of the vehicle is decreasingand there is no torque demand placed on the engine. This approachadvantageously increases the generating capacity of the arrangementfurther for conditions where energy requirements are raised.

For those embodiments of the supercharger assembly in which the dualgenerator is arranged to be operated as a motor to drive the firstarmature, and the generator and motor are arranged to cooperate when theepicyclic gear train is locked using the second clutch, thereby tosupply a drive force to a vehicle engine, the method may compriseengaging the first clutch and locking the epicyclic gear train using thesecond clutch, and subsequently using the drive force to restart theengine following a cessation of engine operation. In this way, thesupercharger assembly may be operated as a BISG. Additionally, themethod may comprise engaging the first clutch and locking the epicyclicgear train using the second clutch, and using the drive force to providemotive power to the vehicle. In this way, the supercharger may beoperational to act as a micro-hybrid to propel the vehicle over shortdistances.

According to a further aspect of the invention, there is provided avehicle comprising an exhaust-driven turbocharger and a superchargerassembly as described above, in which the supercharger assembly and theturbocharger are arranged to operate sequentially.

The vehicle may be arranged to use the turbocharger and not thesupercharger if the engine speed is above a first threshold. As theturbocharger offers a reduction in fuel consumption compared with thesupercharger assembly, this arrangement beneficially ensures that whenengine speed is sufficient to drive the turbocharger regardless ofoperating conditions, the turbocharger is always used.

The vehicle may be arranged to use the supercharger and not theturbocharger if the engine speed is below a second threshold, whereinthe second threshold is lower than the first threshold. This ensuresthat the supercharger is automatically used when the engine speed isinsufficient to drive the turbocharger.

According to another aspect of the invention, there is provided a methodfor operating a vehicle as described above, wherein the method comprisesuncoupling the first armature from the gear train when the engine speedis above the first threshold.

The invention also extends to a method of operating a vehicle asdescribed above, wherein the method comprises coupling the firstarmature to the gear train when the engine speed falls below the secondthreshold.

The invention also extends to a method of operating a vehicle asdescribed above, wherein the method comprises uncoupling the firstarmature from the gear train during steady-state engine operatingconditions when the engine speed is above the second threshold speed,and when the vehicle is towing a relatively high load.

For those embodiments of the vehicle having a supercharger assemblyincluding a second clutch, the invention also extends to a methodcomprising coupling the first armature to the gear train and unlockingthe gear train during a period of increasing torque demand upon theengine when the engine is operating below the first threshold speed.

According to a further aspect of the invention, there is provided amethod for operating a supercharger assembly of a vehicle, wherein thesecond armature provides additional generating capacity when the firstclutch is engaged, and wherein the method comprises disengaging thefirst clutch when the additional generating capacity is not required.The generator may further comprise a third armature which is coaxialwith the first and second armatures, and a second clutch between thethird armature and the second armature. The third armature may be drivenby the second armature on engagement of the second clutch, wherein thethird armature provides additional generating capacity to the generatorwhen coupled to the second armature when both the first and secondclutches are engaged, and wherein the method comprises disengaging thesecond clutch when the additional generating capacity from the thirdarmature is not required.

According to another aspect of the invention, there is provided avehicle having a supercharger assembly as described above.

According to another aspect of the invention, there is provided avehicle having a control unit as described above.

According to an aspect of the invention there is provided a dualgenerator of a vehicle comprising co-axial relatively rotatablearmatures, and a disengageable clutch between the armatures, one of saidarmatures being adapted for permanent drive from a source of motivepower, and the other of said armatures being driven by said one armatureon engagement of said clutch.

The dual generator allows for electrical and mechanical connection of asupercharger on demand, thus avoiding idle rotation thereof. The sourceof motive power is typically a vehicle internal combustion engine. Inone embodiment the dual generator comprises a primary generatorcomprising said one armature for supplying conventional vehicle systems,and a secondary generator comprising said other armature for supplyingan electric motor of a supercharger.

Another aspect of the invention provides a vehicle supercharger assemblycomprising a dual generator of the invention, an epicyclic gear train,an electric motor and a supercharger impeller, said other armaturedriving said impeller mechanically via the annulus and planets of theepicyclic gear train, said electric motor driving the planet carrier ofthe epicyclic gear train, and said electric motor being electricallydriven on demand from a generator comprising said other armature.

It will be understood that in addition to providing supercharging ondemand, the dual generator arrangement allows for supercharged andnon-supercharged variants of a vehicle engine, but with a common primarygenerator. Furthermore the secondary generator may be varied in capacityfor driving different superchargers associated, for example withgasoline and diesel derivatives of the same basic engine.

According to a further aspect of the invention there is provided acontrol system for a supercharger assembly, a method of preparing foroperation of a supercharger assembly, and a method of operating asupercharger assembly.

In another aspect the dual generator of the invention may be operated asa motor in order to drive the vehicle engine, for example as a beltintegrated starter generator (BISG) or as an anti-stalling measure.

The dual generator can provide additional driving capacity which may notbe available from a conventional generator sized only to meet the normalelectrical load of a vehicle.

Within the scope of this application it is expressly envisaged that thevarious aspects, embodiments, examples and alternatives set out in thepreceding paragraphs, in the claims and/or in the following descriptionand drawings, and in particular the individual features thereof, may betaken independently or in any combination. For example, featuresdisclosed in connection with one embodiment are applicable to allembodiments, except where such features are incompatible.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the present invention will now be described, by way ofexample only, with reference to the accompanying drawings, in which likecomponents are assigned like numerals, and in which:

FIG. 1 is a schematic end elevation of a generator/superchargerassembly, representing both a prior art arrangement and an embodiment ofthe present invention;

FIG. 2 is an axial cross-section on line A-A of FIG. 1 for the casewhere the generator/supercharger assembly is an arrangement which isknown in the prior art;

FIG. 3 is an axial cross-section on line A-A of FIG. 1 for the casewhere the generator/supercharger assembly is an arrangement according toan embodiment of the invention including a first clutch and a secondclutch;

FIG. 4 is a graph which indicates the engine operating range of thearrangement shown in FIG. 3;

FIG. 5 is a table which outlines an embodiment of a control regime whichmay be used with the arrangement shown in FIG. 3;

FIG. 6 is a rearrangement of the table in FIG. 5, in which differentcontrol scenarios have been grouped according to differentconfigurations of the arrangement shown in FIG. 3;

FIG. 7 is a flow diagram illustrating a process for implementing thecontrol regime in FIG. 5;

FIG. 8 is an illustration of a vehicle comprising the superchargergenerator arrangement in FIG. 3; and

FIG. 9 is an axial cross-section on line 2-2 of FIG. 1 for the casewhere the generator/supercharger assembly is an alternative embodimentto that in FIG. 3, in which only the first clutch is provided.

DETAILED DESCRIPTION

With reference to FIGS. 1 and 2, a conventional supercharger generatorarrangement 10 comprises a drive pulley 12, driven by a conventionalserpentine auxiliaries drive belt of a vehicle engine (not shown). Thepulley 12 is coupled to an armature 14 of a vehicle generator, e.g. analternator. The generator armature 14 is in turn coupled to an annulus16 of an epicyclic gear train, comprising a gearing mechanism havingplanets 18, and a sun 20 directly connected to a drive shaft 22 of animpeller 24 of a supercharger. The planets 18 are rotatably mounted on aplanet carrier 26, which is connected to an armature 28 of an electricmotor, which surrounds the drive shaft 22. The planets 18 mesh with boththe annulus 16 and the sun 20, such that if the planet carrier 26 isheld stationary, rotation of the annulus 16 causes both the planets 18and the sun 20 to rotate. The impeller 24 is coupled to the sun 20 viathe drive shaft 22, and therefore when the sun 20 rotates, the impeller24 also rotates. The impeller 24 is located within a chamber (not shown)forming part of an air inlet system for the vehicle engine. When theimpeller 24 rotates, this acts to raise the pressure, temperature anddensity of the engine inlet air in the inlet manifold, which increasesperformance of the engine as described earlier. The magnitude of thepressure, temperature and density rise of the inlet air is determinedprimarily by the rotational speed of the impeller 24.

The components of the supercharger generator arrangement 10 are arrangedco-axially about a common axis of rotation 30, and the impeller driveshaft 22 is journalled in a cavity 31 which is formed at the centre ofthe annulus 16 as illustrated. Other components, such as the stators ofthe generator and motor, and the supercharger housing, are notillustrated, but will be understood to be necessary and form no part ofthe present invention, as such. The motor armature 28 is mounted so asto rotate with the planet carrier 26, and independently of the othercomponents of the supercharger generator arrangement 10, according to adrive force supplied by the electric motor.

In use, when the vehicle engine is running, the auxiliaries drive beltdrives the pulley 12, causing it to rotate about axis 30. The angularspeed at which the pulley 12 rotates is typically three times thevehicle engine speed, due to the ratio of the diameter of the pulley 12to the diameter of a corresponding pulley on the engine (not shown)which drives the auxiliaries drive belt. The rotation of the pulley 12in turn causes the generator armature 14 to rotate, thereby generatingelectrical energy in the generator. Additionally, the annulus 16 of theepicyclic gearbox, which is coupled to the generator armature 14 and thepulley 12, is rotated at the same angular speed as the pulley 12. If themotor armature 28 and the planet carrier 26 are held stationary whilethe annulus 16 rotates, the planets 18 are rotated by the rotatingannulus 16. The planets 18 rotate in the same sense as the annulus 16,although at a higher angular speed, because of their smaller diameter.Rotation of the planets 18 gives rise to rotation of the sun 20, thedrive shaft 22 and the impeller 24, but in the opposite sense. Theangular speed at which the impeller 24 rotates is therefore determinedby the gear ratio of the sun 20 to the planets 18, and also the gearratio of the planets 18 to the annulus 16. Typically, the components ofthe epicyclic gearbox are arranged to provide an overall gearing ratioof approximately ten to one. Therefore, when the motor armature 28 isheld stationary, the angular speed at which the impeller 24 rotates isten times that of the pulley 12, and therefore thirty times that of thevehicle engine. As noted previously, this provides a typical range ofspeed for the impeller 24 of between 15,000 and 210,000 rpm.

As mentioned earlier, it is generally desirable to control the speed ofthe impeller 24 within a much smaller range than this, at around 120,000rpm, in order to provide optimal performance. Therefore, the motorarmature 28 is driven by the motor in order to adjust the rotationalspeed of the impeller 24. If the vehicle engine speed is low, such thatthe speed of the impeller would be too low if the planet carrier 26remained stationary, the motor turns the motor armature 28 and theplanet carrier 26 in the opposite sense to the rotation of the annulus16. This increases the rotational speed of the annulus 16 relative tothe centres of the planets 18. This causes the planets 18 to move aroundthe annulus 16 faster and therefore rotate about their own axes with ahigher angular speed, which in turn increases the angular speed of thesun 20 and the impeller 24. In this way, the rotational speed of theimpeller 24 is increased to its optimal level when the vehicle enginespeed is low.

Correspondingly, if the engine speed is high, such that the rotationalspeed of the impeller 24 would be too high if the planet carrier 26remained stationary, this is compensated for by rotating the motorarmature 28 and planet carrier 26 in the same sense as the annulus 16,albeit at a slower rotational speed than that of the annulus 16. Thisreduces the rotational speed of the annulus 16 relative to the centresof the planets 18, and therefore reduces the speed at which the sun 20and in turn the impeller 24 are rotated. In this way, the rotationalspeed of the impeller 24 is decreased to its optimal level when thevehicle engine speed is high.

A control system is provided in the vehicle, for example in a standardengine management unit (EMU), which determines the operation of thesupercharger generator arrangement 10. Typically, when not in use, thesupercharger is unloaded by opening the chamber in which the impeller 24is located to atmosphere, and the epicyclic gear train idles with thesupercharger impeller 24. When required, the supercharger is broughton-load, for example by closing a vent on the air chamber, and the speedof the supercharger impeller 24 is controlled as described above.

The generator capacity is chosen so that a sufficient electrical reserveis provided to meet normal vehicle requirements and the additionaldemand of the electric motor. Normal maximum vehicle demand may be about2.5 kW, and the maximum demand of the motor armature 28 about 3 kW. Itwill thus be understood that the rotating mass of the generator armature14 is substantially greater than for a non-supercharger variant.

FIG. 3 illustrates an embodiment of the invention, in which asupercharger generator arrangement 110 having a dual clutch system isprovided. The arrangement 110 includes a first clutch 32 which isassociated with the generator, and a second clutch 34, which isassociated with the epicyclic gear train and therefore the superchargerimpeller 24.

The first clutch 32 provides the ability to isolate the generator end ofthe supercharger generator arrangement 110 from the supercharger end. Inthis embodiment, the generator armature 14′ is divided into twoportions: a first armature 14 a which is coupled to the pulley 12; and asecond armature 14 b which is coupled to the annulus 16 of the epicyclicgear train. In this way, the generator armature 14′ is arranged as adual generator with variable generating capacity, with the firstarmature 14 a being arranged for permanent drive from a source of motivepower such as the vehicle engine via the pulley 12, although it will beappreciated that the first armature 14 a is not driven via the pulley 12when the vehicle engine is not running. The first armature 14 a isassociated with the vehicle engine, and the second armature 14 b isassociated with the supercharger. Accordingly, the first armature 14 ais sized to suit the normal vehicle demands, and the second armature 14b is sized to provide the additional electrical energy which is requiredto drive the motor armature 28, which in this arrangement is a thirdarmature, when the supercharger impeller 24 is operational. The secondarmature 14 b is formed with a projection 36 which is rotatably andslidably received in a corresponding recess 38 formed in the firstarmature 14 a, but this is only one of several possibilities forensuring rotation on the axis 30. Thus, with this embodiment, theconventional generator described above is divided so that, in effect,two units are provided, each capable of independent operation.

The stator of the generator is not illustrated in FIG. 3, but in thisembodiment both generator armatures 14 a, 14 b have a common stator. Thecommon stator may include a respective winding for each of the generatorarmatures 14 a, 14 b. In other embodiments, each generator armature 14a, 14 b has a respective stator.

The first and second armatures 14 a, 14 b are coupled by means of thefirst clutch 32, which in this embodiment comprises first and secondfacings 40, 42. In this way the second armature 14 b is arranged to bedriven by the first armature 14 a when the first clutch 32 is engaged.The facings 40, 42 engage on demand, through the action of an actuatingmechanism (not shown) to couple the second armature 14 b for rotationwith the first armature 14 a. Thus, the first clutch 32 of thisembodiment operates as a friction clutch. However, any suitable clutchdevice may be employed, including for example those employingmagneto-rheological fluids which are familiar to the skilled person.

In use, the first clutch 32 is disengaged when the additional generatingcapacity of the second armature 14 b and/or operation of thesupercharger impeller 24 are not required, in which case the secondarmature 14 b, epicyclic gear train and supercharger impeller 24 are notdriven, and typically stationary. As a result, the fuel consumption ofthe vehicle engine is reduced, because the windage, churning andfriction associated with rotation of the supercharger components areavoided. Also, since the second armature 14 b is disengaged from thefirst armature 14 a, the rotational inertia of the generator armature14′ is also substantially reduced as compared with the conventionalarrangement, thereby allowing a more rapid change of engine speed. Thisarrangement is desirable, as the power requirements upon the generatorare greatly reduced when the supercharger impeller 24 is not operating,since there is no need to expend energy by rotating both generatorarmatures 14 a, 14 b. Thus, when the supercharger is not being used, thegenerator is not generating excess electrical energy which is notrequired at that moment. Therefore, fuel consumption is further reduced.

When the supercharger is required, the first clutch 32 is engaged bybringing the first and second facings 40, 42 into contact with oneanother using the actuating mechanism. The second armature 14 b is thencaused to rotate with the first armature 14 a, which in turn drives theepicyclic gear train. The motor armature 28 is driven electrically bythe generator at a speed and rotational sense appropriate to the desiredoutput of the supercharger. Therefore, when the first clutch is engaged,or closed, the supercharger generator arrangement 110 operates inexactly the same manner as the prior art arrangement 10 described above.

The second clutch 34 operates to lock the planets 18 to the annulus 16,thus preventing relative rotation of the planets 18 and the annulus 16.In this way, the second clutch 34 acts to lock the epicyclic gear train.In this embodiment, the second clutch 34 is provided in the form of adog clutch, so that rotation of the planets 18 is prevented by thesecond clutch 34 through interference, and not by friction. The secondclutch 34 comprises a main body 44 which is attached to the annulus 16,between an inside face of the annulus 16 and the planets 18. The annulus16 is formed with an annular chamber 46 which surrounds the cavity 31within which the drive shaft 22 is received. The main body 44 of thesecond clutch 34 is formed with a projection 48 on its inner edge whichextends into the annular chamber 46. The main body 44 comprises a dog 50which extends from an outer edge of the main body 44. Each of theplanets 18 includes a recess 52 which is arranged to receive the dog 50of the second clutch 34. In this embodiment, there is a single dog 50,which engages the nearest planet 18, although in other embodiments thesecond clutch 34 comprises a respective dog 50 for each planet 18.

The extension 48 of the main body 44 is slidably received in the annularchamber 46, such that the main body 44 is able to move towards and awayfrom the planets 18. This movement may be effected by supplyinghigh-pressure oil into the space between the extension 48 and an endface of the annular chamber 46. The oil is conveniently supplied by apump (not shown) to distribute oil throughout the prior art superchargergenerator arrangement 10. The oil penetrates the space beyond theextension 48 of the main body 44 through a channel 54 which is formed inthe body of the annulus 16. A spring 56 is provided on the opposite sideof the extension 44 to the high pressure oil. The spring 56 is retainedby a circlip 57 and acts as a return mechanism to urge the main body 44back into the annular chamber 46 when the high pressure oil is removed.

When the second clutch 34 is open, and the main body 44 is in aretracted position away from the planets 18, the planets 18 are free torotate. When the main body 44 is moved towards the planets 18 into aclosed position under the action of high-pressure oil, the dog 50engages with a recess 52 in one of the planets 18, which prevents theplanets 18 from rotating. In this way, the second clutch 34 disengagesor disables the epicyclic gear train.

When the second clutch 34 is closed and the epicyclic gear train isdisabled, this causes the entire supercharger generator arrangement 110to rotate together at the same speed. In particular, in this situation,the motor armature 28 is forced to rotate at the same speed as both theimpeller 24 and, if the first clutch 32 is closed, the pulley 12.Therefore, when the second clutch 34 is closed, the motor armature 28may be driven by either the impeller 24 or the pulley 12, depending onthe vehicle operating conditions. Closing the second clutch 34 mayadditionally be viewed as effectively coupling the motor armature 28 tothe second armature 14 b. In this way, the motor armature 28 can be usedas a secondary generator in certain situations to increase overallgenerating capacity. Therefore, the system provides a triple generatorarrangement in certain circumstances which beneficially offers anincreased charging rate of the vehicle battery when the two generatorscooperate.

Alternatively, the generator armature 14′ may be operated in reverse toact as a motor and provide drive to the vehicle, either to re-start thevehicle engine, or to drive the vehicle directly over short distances.This may be useful, for example, if the engine is stopped and thenre-started again within a short time period while the engine is stillhot, for example when the vehicle is sitting in slow-moving traffic, orwaiting at traffic lights. In this situation, the generator may be usedas a belt-integrated starter-generator (BISG), to restart the vehicleengine after each cessation of vehicle movement. Restarting the enginein this way is far more fuel-efficient that a cold-start procedure.Therefore, such a system and control strategy can be used to save fuelin, city driving where stops are frequent, and stopping the enginereduces the amount of time that it spends idling. However, the use ofthe generator armature 14′ in this way is dependent on the enginecomponents still being hot such that the engine is easier to start. Inparticular, when the engine lubricating oil is hot it is more effective,which means that the frictional forces which must be overcome in orderto start the engine are reduced. If the engine cools too much, forexample if the vehicle is stopped for a more extended time period, thenthe drive belts will not cope with the increased forces required torestart the engine. As such, using the generator in this way is limitedto situations where the engine is still hot.

Furthermore, a generator may be used as a motor to provide ananti-stalling mechanism, where a region of the engine operating map maytend towards stalling; by this means a minimum engine speed ismaintained until the vehicle engine moves into a different region of theengine operating map.

Generally, a vehicle generator may be over-sized in order to also servein BISG or anti-stalling mode. The ability to effectively couple thegenerator armatures 14 a, 14 b to the motor armature 28 by closing boththe first and second clutches 32, 34 enables the motor armature 28 toprovide additional power for performing the restart function describedabove. This may minimise the amount by which the size of the vehiclegenerator must be increased in order to provide the BISG functionality.The dual generator arrangement, in conjunction with the secondarygenerator, provides additional motor capacity for BISG or anti-stalling,at minimal additional cost, it being understood that in both these modesof use supercharging is not required. It will also be understood thatwhilst the supercharger is unloaded, motive power can be provided notonly from motors comprising the armatures 14 a, 14 b, but also from themotor armature 28.

In a further refinement, the generator armature 14′ together with themotor armature 28 may be used to drive the normal internal combustionengine as a micro-hybrid, optionally in conjunction with the motorarmature 28 of the supercharger. Such an arrangement, dependent upon thecapacity of the vehicle battery, may provide short term motive power orassistance for the vehicle; in particular in low speed city driving.When the armatures 14, 28 are driven, the vehicle engine effectivelyfreewheels, and the torque is passed to the transmission to propel thevehicle. It will be appreciated that using the armatures 14, 28 to drivethe engine in this way consumes a considerable amount of energy, thusthe range over which the vehicle may be propelled in this manner islimited.

The skilled person will appreciate that a supercharger may be requiredfor a relatively short proportion of engine running time; accordingly aconsiderable saving of fuel is possible by elimination of windage,churning and friction losses through the ability to disengage thesupercharger when it is not required.

The supercharger generator arrangement 110 also allows for engagement ofthe first clutch 32 in anticipation of a requirement for operation ofthe supercharger impeller 24, thus bringing the supercharger impeller 24up to speed in advance of loading the impeller 24 in the chamber andenabling operation thereof. The EMU may, for example, monitoraccelerator pedal position and/or rate of change of accelerator pedalposition, and signal engagement of the first clutch 32 just beforesupercharging is required. The motor armature 28 may also be driven forthis purpose from the permanently driven generator (i.e. armature 14 a)since the additional electrical requirement is low because thesupercharger is unloaded.

Thereafter, typically a moment later, the supercharger is brought onload, and the motor armature 28 is driven from the generator associatedwith the second armature 14 b. By this means the supercharger impeller24 may be driven, whilst unloaded, at a speed appropriate for instantsupercharging, if required.

In an alternative embodiment the second armature 14 b may be drivendirectly, for example powered by a vehicle battery or from thepermanently driven first armature 14 a, to bring the second armature 14b up to a speed compatible with the speed of the first armature 14 a.Such an arrangement both reduces the engagement loading on clutchfacings 40, 42, and speeds up the impeller 24 ready for supercharging.

This embodiment relies upon the use of a rotary electrical machine asboth generator and motor, which can be readily accomplished withappropriate design and controls. When supercharging is required, themotor comprising armature 14′ may be converted instantly into agenerator for supplying energy to power the supercharger motor 28.

The desired speed or output of the supercharger of any embodiment may begiven by an algorithm or look-up table of a memory of the EMU, accordingto empirical testing of a particular engine configuration, and the motor28 driven accordingly by a suitable control system.

Where speed of the armatures 14 a, 14 b can be matched by utilizing thearmature 14 b in a motor, it will be understood that a dog clutch may beused to replace the progressive engagement provided by a friction clutchor a magneto-rheological coupling, or the like. Such an arrangement maypermit a more instant response, and be less complex. A dog clutch mayinclude a speed matching device, such as is provided in a synchromeshhub of a vehicle gearbox.

With reference to FIGS. 4, 5 and 6, a control regime according to anembodiment of the invention, which is to be applied to theabove-described supercharger generator arrangement 110 is illustrated.This embodiment of the control regime applies when the superchargergenerator arrangement 110 is used in conjunction with a turbocharger.FIG. 4 shows the duty cycle for the supercharger impeller 24 throughouta typical engine operating range for a vehicle. As shown in the graph,the impeller 24 is regularly operational in the range of 750 to 2000rpm. This is because at these low engine speeds the speed of the engineexhaust gases is too low to provide sufficient power to drive theturbocharger. Therefore, the supercharger is used in order to eliminate“turbo lag”, as described previously.

In the 2000 to 4000 rpm range, the supercharger is used intermittently;normally the turbocharger operates effectively at these engine speeds.However, if there is a sudden change in torque demand, there may be alag as the turbo catches up. This may happen, for example, duringacceleration. Therefore, the supercharger is used during the period ofchanging demand to ensure consistent power delivery from the engine,until the turbocharger has had time to spool up.

Above 4000 rpm, the associated speed of the engine exhaust gases issufficient to drive the turbocharger in most situations, and thereforethe supercharger is rarely used in this range. In this embodiment of thecontrol regime, the supercharger is not used under these operatingconditions, although in other embodiments there may be particularcircumstances in which the supercharger is called into operation, forexample when the throttle is operated particularly aggressively.

FIG. 5 is a table which illustrates how the first clutch 32 and thesecond clutch 34 are operated for a number of different scenarios,according to this embodiment of the control regime. The tableadditionally indicates whether the armature 28 of the electric motor isused to drive the planets 18 in each scenario. It should be noted thatthere are three states for the armature 28: “driven” in which thearmature 28 is driven electrically to turn the planets 18 for thepurpose of adjusting the rotational speed of the impeller 24; “notdriven” in which the armature 28 is idle and free to rotate in eithersense and at any speed; and “acting as additional generator” in whichcase the armature 28 is locked to the annulus 16 through the closure ofthe second clutch, so that the armature 28 may be driven by the impeller24 or the pulley 12 to act as an additional generator as describedabove. More detailed explanations of each scenario are outlined below.

A “cold-start” scenario refers to starting the vehicle engine using astarter motor when the engine is cold, i.e. when it has not been usedfor more than a few minutes. During a cold-start procedure, thesupercharger is not used, as this would place unnecessary strain onengine components. Also, there is no need to use the supercharger duringa cold-start, as the vehicle is not moving and therefore there is notorque demand placed on the engine. Accordingly, as shown in FIG. 5,during a cold-start procedure, both the first clutch 32 and the secondclutch 34 are open. Additionally the motor armature 28 does not drivethe planets 18. By opening the first clutch 32 at this time thesupercharger is disengaged, and therefore the vehicle does notunnecessarily expend energy driving the second armature 14 b and thesupercharger impeller 24, thereby improving fuel efficiency during thecold-start procedure.

As neither the supercharger components nor the motor armature 28 aredriven during a cold-start procedure, it does not particularly matterwhether the second clutch 34 is open or closed during the cold-start.However, the next step after a cold-start is for the vehicle to pullaway. Therefore, by arranging for the second clutch 34 to be open duringa cold-start, the second clutch 34 is placed in the correct position inreadiness for when the vehicle needs to pull away. As the vehicle pullsaway, a torque demand is placed on the engine, at which time thesupercharger impeller 24 is called into operation. Therefore, the secondclutch 34 needs to be open when the vehicle is pulling away. If thesecond clutch 34 were closed initially when the engine received thetorque demand, the second clutch 34 would first need to be opened beforethe supercharger impeller 24 could operate. Therefore, by opening thesecond clutch 34 during a cold-start, the vehicle may offer improvedresponsiveness in the event that an initial torque demand is placed onthe engine.

It is noted that in this embodiment of the control regime, in all caseswhere the first clutch 32 is open, the motor armature 28 is not driven.This is because the motor armature 28 does not have sufficient power todrive the impeller 24. Also, when the first clutch 32 is open, thesecond armature 14 b and the annulus 16 can rotate freely. Therefore,driving the motor armature 28 in this scenario would result inunpredictable movement of the gear train components. In particular, ifthe second clutch is open, the impeller 24 is also free to rotatesemi-independently of the motor armature 28. Therefore, driving themotor armature 28 may simply result in the armature 28 and planets 18rotating while the impeller 24 and annulus 16 remained relativelystationary, thereby wasting energy.

A “hot-start” scenario refers to what is commonly known as “stop-start”,in which the vehicle engine uses the generator as a motor in certainconditions, as described previously. As shown in FIG. 5, during ahot-start procedure, both the first clutch 32 and the second clutch 34are closed. By closing the first clutch 32, both the first and thesecond armatures 14 a, 14 b may be driven by the generator, andtherefore enabling the full capacity of the generator to be utilised forproviding a drive force. In addition to this, as the second clutch 34 isclosed, the motor armature 28 may be driven in cooperation with thegenerator armature 14, in order to maximise the drive force available.This drive force is used to drive the pulley 12, thus driving theauxiliaries drive belt, and therefore re-starting the engine.

Alternatively, in another embodiment the generator armature 14′ and themotor armature 28 are used in cooperation to drive the vehicle overshort distances, thus acting as a micro-hybrid as described above. Thisarrangement is equivalent to a “hot-start” except for the fact that theengine is not supplied with fuel in order to commence normal operation,instead the generator armature 14′ and the motor armature 28 continue todrive the engine in order to provide torque to the vehicle transmissionto propel the car. Accordingly, the configuration for the superchargergenerator arrangement 110 in this scenario is the same as for a“hot-start”, and therefore is not listed separately in FIG. 5.

In “idle” the engine is running but the vehicle is not moving.Therefore, there is no torque demand placed on the vehicle, so thesupercharger is not required. In order to minimise the fuel consumptionof the engine when idling, the first clutch 32 is opened to isolate thepulley 12 from the second armature 14 b, the epicyclic gear train andthe impeller 24, thus minimising the load attached to the engine.Therefore, only the first armature 14 a is rotated when idling, whichmeans that the generator produces only the energy which is required fornormal operation, and does not burden the engine by generating excesselectrical energy which is not required at that time.

FIG. 5 indicates that the arrangement of the second clutch 34 is notapplicable in idling conditions. However, as described above, the secondclutch 34 is preferably open at this time, such that the second clutch34 is ready for a new torque demand being placed on the vehicle engine.

The “idle after start low ambient” condition shown in FIG. 5 relates toa particular condition where the engine is idling and the ambienttemperature is low. Under such conditions, the normal power requirementsof the vehicle may be increased in order to heat the interior of thevehicle. In normal idling conditions, the engine idles at low speed, andtherefore the generator does not produce much electrical energy.Therefore, in order to improve the generating capacity of the generatorwhen the power requirements are raised, both the first clutch 32 and thesecond clutch 34 are closed. By closing the first clutch 32, the secondarmature 14 b is coupled to the first armature 14 a, thereforeincreasing the generating capacity of the generator. By also closing thesecond clutch 34, the generator armature 14′ is effectively coupled tothe motor armature 28, such that the two rotate together. The motorarmature 28 is not driven at this point; instead it is used as anadditional generator, to further increase the generating capacity of thevehicle as described previously.

The “steady state−low load<4000 rpm” condition relates to when a vehicleis cruising at a substantially constant speed, with an engine speedbelow 4000 rpm. When the vehicle is travelling at a constant speed, thetorque demand placed on the engine is relatively low. Therefore, thesupercharger impeller 24 is not loaded at this point as the additionaltorque which it provides is not required. In order to avoid the impeller24 idling and therefore wasting energy and consuming additional fuel,the first clutch 32 is opened. In this way, the impeller 24 isdisassociated from the engine, and is therefore not drivenunnecessarily. As the first clutch 32 is open, the motor armature 28 isnot driven at this stage for the reasons described above. Specifically,in this condition there is no requirement for the impeller 24 to bedriven, and therefore there is no reason to drive the motor armature 28.If the engine speed is sufficient, towards the higher end of the rangefor this condition, the turbocharger may be used, primarily in order toimprove the operating efficiency of the engine by extracting energy fromthe exhaust gases.

The “steady state−high load<1500 rpm” condition relates to circumstancesin which a high load is placed on the vehicle, but the engine speed iskept low. For example, this could relate to a scenario in which avehicle is towing a load in a high gear. This example applies mainly tovehicles provided with a manual gearbox, as an automatic gearbox wouldnormally shift into a lower gear when towing in order to avoid stalling.

In this situation, the torque demand placed on the engine is relativelyhigh, but the engine speed is too low for the turbocharger to operateeffectively. Therefore, the supercharger impeller 24 is loaded in thechamber and driven in order to increase engine performance. To achievethis, the first clutch is closed 32, the second clutch 34 is opened andthe motor armature 28 is driven, such that the impeller 24 is driven inthe normal manner described previously.

“Steady state>4000 rpm” refers to situations where the vehicle iscruising at a substantially constant speed, and the engine speed isabove 4000 rpm. In general this relates to cruising at high speed, forexample in motorway driving. As the engine speed is high, theturbocharger is used in order to improve the fuel economy and to provideany additional power which may be required. Therefore, the superchargeris deactivated in the same way as for the “steady state−low load<4000rpm” condition.

The “transient<4000 rpm” mode relates to a condition where there is asudden change in torque demand when the engine speed is below 4000 rpm.When the engine is running below this speed, the turbocharger is runningat a relatively low speed. When the torque demand changes, for exampleif the driver opens the throttle, the engine responds by rapidlyincreasing the engine speed. The turbocharger cannot speed up at thesame rate as the engine, and therefore there will be a differencebetween the desired manifold pressure and the actual manifold pressureas the turbocharger catches up with the engine, resulting in “turbolag”. The supercharger can be used to alleviate this problem, bymaintaining the required manifold pressure during the time that theturbocharger is spooling up. Therefore, for this condition the firstclutch 32 is closed, the second clutch 34 is open, and the motorarmature 28 is driven, so that the supercharger operates to drive theimpeller 24 in the normal way, as described previously.

The “transient>4000 rpm” relates to a similar condition to thepreviously described “transient<4000 rpm” condition, with the differencebeing that the engine speed is above 4000 rpm. When the engine isrunning above this speed, the turbocharger is also running at arelatively high speed. Therefore, if there is a change in the torquedemand, and therefore a change in the required manifold pressure, theturbocharger is able to meet these demands without falling behind theengine with a resulting “turbo lag”. Therefore, the supercharger is notrequired in this situation. As such, the first clutch 32 is opened, todisassociate the supercharger from the engine and minimise the load onthe engine by preventing the supercharger from idling. Accordingly, themotor armature 28 is not driven, for the reasons described previouslyfor when the first clutch 32 is open. The second clutch 34 may be eitheropen or closed in this situation as the gear train is not being driven.However, as the vehicle is moving at high speed in this scenario, it islikely that the supercharger will not be required again until thevehicle has slowed significantly. Therefore, it may be preferable tohave the second clutch 34 closed, in readiness for using thesupercharger generator arrangement 110 in “Regen Mode” as the vehicleslows, which is described below.

“Regen Mode” relates to a situation where a vehicle is slowing downunder engine braking. As the engine continues to turn, the pulley 12 isrotated. Therefore, there is an opportunity to extract some energy fromthe system which would otherwise be wasted, by using the rotation of thepulley 12 to generate electrical energy to be stored in the vehiclebattery. In order to extract as much energy as possible, the controlregime is arranged to optimise the generating capacity of thesupercharger generator arrangement 110 by using both the first armature14 a and the second armature 14 b, as well as using the motor armature28 as an additional generator. Therefore, both the first clutch 32 andthe second clutch 34 are closed, so that the first armature 14 a, thesecond armature 14 b, and the motor armature 28 are all effectivelycoupled together. In this way the armatures 14 a, 14 b, 28 can cooperateto generate electrical energy in the same way as for the “idle afterstart low ambient”.

FIG. 7 illustrates a process 58 for implementing the above-describedcontrol regime. In this embodiment, the process 58 is conducted by theEMU. The EMU identifies at step 60 the current operating condition asdefined above with reference to FIG. 5. The EMU then determines at step62 the appropriate configuration for the supercharger generatorarrangement 110 for the condition identified at step 60. The EMU thenchecks at step 64 whether the supercharger generator arrangement 110 isconfigured correctly. If the arrangement 110 is configured correctly,the process 58 ends at step 68. If the arrangement 110 is not configuredcorrectly, the EMU reconfigures at step 66 the supercharger generatorarrangement 110 accordingly. The process 58 then ends at step 68.

As shown in FIG. 8, the invention also extends to a vehicle 70comprising a supercharger generator arrangement 110 as described above.

As illustrated in FIG. 9, the invention also extends, in an alternativeembodiment, to a supercharger generator arrangement 120 which isprovided with a first clutch 32 only. The second clutch 34 of thepreviously described embodiments is not included in this embodiment,however, the supercharger generator arrangement 120 of this embodimentis otherwise identical to the arrangement 110 of FIG. 3. In particular,as with the above described embodiments, the generator armature 14′ isdivided into first and second armatures 14 a, 14 b, and the first clutch32 is used to selectively couple the first armature 14 a to the secondarmature 14 b. Thus, this embodiment provides a variable generatingcapacity in the same way as the previously described embodiments.

As this embodiment does not include the second clutch 34, the option toeffectively couple the motor armature 28 to the generator armature 14′is not available. Therefore, the control regime described previouslywith reference to FIG. 5 is limited for the arrangement 120 of thisembodiment, such that only those scenarios in which the second clutch 34is open (or not applicable) are possible. Therefore, this arrangement120 is not able to operate in the “hot start”, “idle after start lowambient” or “Regen” modes.

It will be appreciated by a person skilled in the art that the inventioncould be modified to take many alternative forms to that describedherein, without departing from the scope of the appended claims.

Embodiments of the present invention may be understood by reference tothe following numbered paragraphs:

-   1. A vehicle supercharger assembly comprising:    -   a dual generator comprising first and second co-axial relatively        rotatable armatures, and a first disengageable clutch between        the armatures, said first armature being adapted for permanent        drive from a source of motive power, and said second armature        being driven by said first armature on engagement of said first        clutch;    -   a supercharcharger impeller, the second armature driving the        impeller mechanically via a gear train;    -   an electric motor coupled to the gear train and operable to        adjust the rotational speed of the impeller;    -   wherein, in use, the electric motor is electrically driven on        demand from a generator comprising the second armature.-   2. A supercharger assembly according to paragraph 1, wherein the    second armature is associated with a generating capacity equal to or    greater than said first armature.-   3. A supercharger assembly according to paragraph 1, wherein the    first and second armatures are journalled one within the other for    rotation about a common axis.-   4. A supercharger assembly according to paragraph 1, wherein the    first clutch is provided axially between said armatures.-   5. A supercharger assembly according to paragraphs 1, wherein one or    both of the first and second armatures comprises an electric motor.-   6. A supercharger assembly according to paragraph 1, wherein the    impeller is co-axial with the first and second armatures.-   7. A supercharger assembly according to paragraph 6, wherein the    impeller is journalled in the second armature.-   8. A supercharger assembly according to paragraph 1, wherein the    dual generator is operable as a dual motor to drive said source of    motive power.-   9. A supercharger assembly according to paragraph 1, wherein the    gear train is an epicyclic gear train.-   10. A supercharger assembly according to paragraph 9 the second    armature driving said impeller mechanically via the annulus and    planets of the epicyclic gear train and said electric motor driving    the planet carrier of the epicyclic gear train.-   11. A supercharger assembly according to paragraph 9, comprising a    second clutch for selectively locking and unlocking the epicyclic    gear train.-   12. A supercharger assembly according to paragraph 11, wherein the    electric motor comprises a third armature which is arranged    coaxially with the first and second armatures;    -   wherein the electric motor provides variable, bi-directional        drive to adjust the rotational speed of the supercharger        impeller when the gear train is not locked.-   13. A supercharger assembly according to paragraph 11, wherein the    second clutch is arranged to lock the epicyclic gear train such that    relative rotation of the planets and the annulus is prevented.-   14. A supercharger assembly according to paragraph 13, wherein the    second clutch is in the form of a dog clutch arranged to interengage    the annulus and at least one of the planets.-   15. A supercharger assembly according to paragraph 14, wherein    disengagement of the dog clutch is effected hydraulically.-   16. A supercharger assembly according to paragraph 11, wherein the    dual generator is arranged to be operated as a motor to drive the    first armature, and the generator and motor are arranged to    cooperate when the epicyclic gear train is locked by the second    clutch, thereby to supply a drive force to a vehicle engine.-   17. A supercharger assembly according to paragraph 11 wherein the    electric motor comprises a third armature which is arranged    coaxially with the first and second armatures, and wherein the third    armature is operable as a secondary generator to increase the    overall generating capacity of the vehicle when the first clutch is    engaged and the epicyclic gear train is locked by the second clutch.-   18. A control unit for a supercharger assembly according to    paragraph 1, and comprising an electronic control unit for    controlling operation of the first clutch and the electric motor,    and for enabling the supercharger.-   19. A control unit for a supercharger assembly according to    paragraph 11, and comprising an electronic control unit for    controlling operation of the first clutch, the second clutch and the    electric motor, and for enabling the supercharger.-   20. A control unit according to paragraph 18, wherein said control    unit determines coupling of said electric motor with the generator    comprising the second armature.-   21. A control unit according to paragraph 18, wherein said control    unit is further adapted to configure said dual generator as a dual    motor adapted to drive said source of motive power.-   22. A method of preparing for operation of a vehicle supercharger    assembly according to paragraph 1, and comprising the steps of:    -   I. detecting a requirement for supercharging,    -   II. engaging the first clutch to mechanically couple the first        and second armatures, and operating the motor to bring the        impeller to a desired speed.-   23. A method according to paragraph 22, wherein said motor is    electrically coupled to a generator associated with said second    armature.-   24. A method of operating a vehicle supercharger assembly according    to paragraph 1, and comprising the preparing method of paragraph 23,    and the further steps of:    -   I. bringing said supercharger on load, and electrically varying        the speed of said motor to maintain the output of said        supercharger at a desired rate.-   25. A method of providing a belt integrated starter generator    comprising configuring the dual generator of a supercharger assembly    according to paragraph 1 as a dual motor, and engaging said first    clutch.-   26. A method of providing an anti-stalling device for an internal    combustion engine, the method comprising the steps of configuring    the dual generator of a supercharger assembly according to paragraph    1 as a dual motor, and engaging the first clutch.-   27. A method according to paragraph 25, comprising operating said    dual motor and said electric motor in unison.-   28. A method of operating a supercharger assembly according to    paragraph 1, the method comprising disengaging the first clutch in    at least one of the following conditions: (a) during an engine    cold-start procedure; and (b) when the vehicle is idling.-   29. A method of operating a supercharger assembly according to    paragraph 11, the method comprising disengaging the first clutch in    any one of the following conditions: (a) during an engine cold-start    procedure; and (b) when the vehicle is idling; the method further    comprising unlocking the epicyclic gear train using the second    clutch when the first clutch is disengaged.-   30. A method of operating a supercharger assembly according to    paragraph 1, the method comprising engaging the first clutch in any    one of the following conditions: (1) when the ambient temperature is    low and the engine is idling; and (2) when the speed of the vehicle    is decreasing and there is no torque demand placed on the engine.-   31. A method of operating a supercharger assembly according to    paragraph 17, the method comprising engaging the first clutch,    locking the epicyclic gear train using the second clutch and    operating the third armature as a secondary generator in any one of    the following conditions: (1) when the ambient temperature is low    and the engine is idling; and (2) when the speed of the vehicle is    decreasing and there is no torque demand placed on the engine.-   32. A method of operating a supercharger assembly according to    paragraph 16, the method comprising engaging the first clutch and    locking the epicyclic gear train using the second clutch, and    subsequently using the drive force to restart the engine following a    cessation of engine operation.-   33. A method of operating a supercharger assembly according to    paragraph 16, the method comprising engaging the first clutch and    locking the epicyclic gear train using the second clutch, and    subsequently using the drive force to provide motive power to the    vehicle.-   34. A vehicle comprising an exhaust-driven turbocharger and a    supercharger assembly according to any one of paragraph 1, wherein    the supercharger assembly and the turbocharger are arranged to    operate sequentially.-   35. A vehicle according to paragraph 34, wherein the vehicle is    arranged to use the turbocharger and not the supercharger when the    engine speed is above a first threshold.-   36. A vehicle according to paragraph 35, wherein the vehicle is    arranged to use the supercharger and not the turbocharger if the    engine speed is below a second threshold, wherein the second    threshold is lower than the first threshold.-   37. A method for operating a vehicle according to paragraph 34, the    method comprising disengaging the first clutch when the engine speed    is above the first threshold.-   38. A method for operating a vehicle according to paragraph 34, the    method comprising engaging the first clutch when the engine speed    falls below the second threshold.-   39. A method for operating a vehicle according to paragraph 36, the    method comprising disengaging the first clutch during steady-state    engine operating conditions when the engine speed is above the    second threshold, and when the vehicle is towing a relatively high    load.-   40. A method for operating a vehicle according to paragraph 35, when    dependent on paragraph 11, the method comprising engaging the first    clutch and unlocking the gear train during a period of increasing    torque demand upon the engine when the engine is operating below the    first threshold.-   41. A method for operating a supercharger assembly according to    paragraph 1, wherein the second armature provides additional    generating capacity when the first clutch is engaged, and wherein    the method comprises disengaging the first clutch when the    additional generating capacity is not required.-   42. A vehicle comprising a supercharger assembly according to    paragraph 1.-   43. A vehicle comprising a control unit according to paragraph 18.

This application claims priority from UK Patent Application No.GB1210679.5, filed 15 Jun. 2012, the entire contents of which areexpressly incorporated by reference herein.

The invention claimed is:
 1. A vehicle supercharger assembly comprising:a dual generator comprising first and second co-axial relativelyrotatable armatures, and a first disengageable clutch between the firstand second armatures, said first armature being permanently driven froma source of motive power when said source of motive power isoperational, and said first and second armatures operating as a singlearmature and rotating at the same speed at all times when said firstclutch is engaged; a supercharger impeller, the second armature drivingthe supercharger impeller mechanically via an epicyclic gear train; asecond clutch for selectively locking, and unlocking the epicyclic geartrain; an electric motor coupled to the gear train and operable toadjust a rotational speed of the supercharger impeller; wherein, in use,the electric motor is electrically driven on demand from the dualgenerator, and wherein disengagement of the first clutch disengages thesecond armature and supercharger impeller from the source of motivepower.
 2. The supercharger assembly according to claim 1, wherein thesecond armature is associated with a generating capacity equal to orgreater than said first armature.
 3. The supercharger assembly accordingto claim 1, wherein the first clutch is provided axially between saidfirst and second armatures.
 4. The supercharger assembly according toclaim 1, wherein one or both of the first and second armatures comprisesan additional electric motor.
 5. The supercharger assembly according toclaim 1, wherein the dual generator is operable as a dual motor to drivesaid source of motive power.
 6. The supercharger assembly according toclaim 1, wherein the epicyclic gear train comprises an annulus, a planetcarrier, and planets, wherein the second armature is configured to drivesaid supercharger impeller mechanically via the annulus and planets ofthe epicyclic gear train, and wherein said electric motor is configuredto drive the planet carrier of the epicyclic gear train.
 7. Thesupercharger assembly according to claim 1, wherein the electric motorcomprises a third armature which is arranged coaxially with the firstand second armatures; wherein the electric motor provides variable,bi-directional drive to adjust the rotational speed of the superchargerimpeller when the epicyclic gear train is not locked.
 8. Thesupercharger assembly according to claim 1, wherein the second clutch isarranged to lock the epicyclic gear train such that relative rotation ofplanets and an annulus of the epicyclic gear train is prevented.
 9. Thesupercharger assembly according to claim 8, wherein the second clutch isa dog clutch arranged to interengage the annulus and at least one of theplanets.
 10. The supercharger assembly according to claim 9, whereindisengagement of the dog clutch is effected hydraulically.
 11. Thesupercharger assembly according to claim 1, wherein the dual generatoris arranged to be operated as a motor to drive the first armature, andthe dual generator and motor are arranged to cooperate when theepicyclic gear train is locked by the second clutch, thereby to supply adrive force to a vehicle engine.
 12. The supercharger assembly accordingto claim 1, wherein the electric motor comprises a third armature whichis arranged coaxially with the first and second armatures, and whereinthe third armature is operable as a secondary generator to increaseoverall generating capacity of the vehicle when the first clutch isengaged and the epicyclic gear train is locked by the second clutch. 13.The supercharger assembly according to claim 1, wherein the secondarmature and the supercharger impeller are isolated from the source ofmotive power when the first clutch is disengaged, permitting freerotation of the second armature and supercharger impeller.
 14. Thesupercharger assembly according to claim 1, wherein the first and secondarmatures are journaled one within the other for rotation about a commonaxis.
 15. A control unit comprising an electronic control unit forcontrolling the supercharger assembly according to claim 1, saidelectronic control unit controlling operations of the first clutch andthe electric motor, and enabling a supercharger of the superchargerassembly.
 16. The control unit according to claim 15, wherein theelectronic control unit controls operation of the second clutch.
 17. Thecontrol unit according to claim 15, wherein said electronic control unitdetermines coupling of said electric motor with the dual generatorcomprising the second armature.
 18. The control unit according to claim15, wherein said electronic control unit is further adapted to configuresaid dual generator as a dual motor adapted to drive said source ofmotive power.
 19. A vehicle comprising the supercharger assemblyaccording to claim
 1. 20. A vehicle according to claim 19, comprising anexhaust-driven turbocharger, wherein the supercharger assembly and theturbocharger are arranged to operate sequentially.